Knurling tool for bowling balls



' G. B. PRICE KNURLING TOOL FOR BOWLING BALLS Filed y 1955 June 10, 1958 United This invention relates to bowling balls and has reference to knurling the finger grips thereof.

In the sport of bowling it is important that the finger cavities within the bowling ball be constructed so that the ball may be firmly held by the fingers, yet easily released. For this purpose it is desirable that knurls be placed within the finger cavities on the gripping surfaces of the fingers so that a firm grip may be held within cavities of relatively large diameter, which large cavities are conducive to unimpaired release. It is likewise important in the sport of bowling that the bowling ball be balanced so that its center of gravity is coincident with its geometrical center. Cutting tools previously used for the purpose of constructing gripping surfaces within the finger cavities of bowling balls remove part of the material from which the ball is constructed, thereby altering the center of gravity. When forming such knurls by conventional tools, pressure against the cutting edge of the tool may cause it meet as a wedge against the inner surface of a finger cavity and thereby weaken the internal structure of the ball and eventually form lines of internal cracking.

An important object of this invention is to provide a tool for the construction of knurls within the finger cavities of bowling balls without causing any alteration in the center of gravity of the ball.

A further object of this invention is to provide a knurling tool for the finger cavities of bowling balls which exerts no appreciable wedging action and subsequent cracking in its operation.

A further object of this invention is to provide a knurling tool for the finger cavities of bowling balls which is capable of forming knurls at various locations upon the inner surfaces of finger cavities.

A further object of this invention is to provide a knurl-' ing tool for the finger cavities of bowling balls which is capable of forming knurls of improved design providing less effort on the part of the bowler when gripping the ball.

In the drawings:

Figure l is a broken sectional view of a bowling ball showing two finger cavities with knurls formed therein in accordance with the invention.

Figure 2 is an elevation of a tool described herein illustrating its operation within the finger cavity of a bowling ball, the latter being shown in broken section.

Figure 3 is a plan view of the upper portion of the tool illustrated in Figure 2.

Figure 4 is a front elevation of a knurled insert for forming the referred to knurls.

Figure 5 is an elevation of a modified form of knurling tool and showing the position of inserts by means of dotted lines.

From the drawings it will be noted that an impression insert formed from metal such as steel or aluminum in the shape of an arcuate semicylindrical sect-or is provided on its outer surface with knurls 11 of crossed threads, the pitch of each being 1 threads per inch.

tent

The inner peripheries at each end of the insert 10 are bevelled as at 12 for carrying out the knurling operation hereinafter described. A compression insert 13 is constructed substantially the same as the impression insert 10 excepting that a smooth exterior surface is provided thereon. accommodated between the interior surfaces of the inserts 10 and 13 is formed with an enlarged base 15 conically inclining inward at an angle corresponding to the inclination at the ends of the inserts and with flat surfaces 16 in the form of parallel planes at its upper end through which a pin 17 projects perpendicularly. A bifurcated circular cam 18 is asymmetrically journaled about the pin 17 and is affixed to an outward extending handle 19. A tubular mandrel 29 having its lower end 21 conically inclined inward and downward corresponding to the conical inclination at the ends of the inserts 10 and 13 and having its upper end flat and perpendicular to its length is slidably mounted on the draw pin 14- so that its upper end engages the periphery of the cam 18 when its lower conical end engages the inserts 1t) and 13 positioned about the draw pin 14.

In the alternate construction shown in Figure 5 the cam and handle mounted at the upper end of the draw pin are replaced by threads 25 on the draw pin 14, and a nut 26 which is fastened thereby and may be tightened by turning upon the threads in a clockwise direction.

In operation, an impression insert 10 is heated by any suitable means such as a gas flame or in an oven; when sufficiently hot to soften hardened rubber or other thermoplastic material used in the construction of bowling'balls, the insert is placed on the draw pin 14 between its base 15 and the-mandrel lit. The compression insert 13 is likewise placed about the draw pin 14 in a position opposite the impression insert 10, and the lower end of the tool, including the inserts, is lowered into a finger cavity 23 of a bowling ball 22 with the hot impression insert 10 facing that side of the cavity which is to be knurled. After the lower portion of the tool has been lowered to a predetermined depth within the finger cavity 23, the cam 18 isrotated about its asymmetric pivotal mountings by means of the handle 19 and the mandrel 20 is depressed so that the inclined surface at its lower end 21 coacts with the inclined inner surfaces 12 at the upper ends of the inserts 10 and 13; at the same time the inclined surface at the base 15 of the draw pin 26 coacts with the inclined inner surfaces 12 at the lower end of the inserts 10 and 13 causing the inserts to be forced outward in opposite directions against the inner surface of the finger cavity 33. The heat contained in the impression insert 10 softens the adjacent inner surface of the finger cavity 23 and reforms" the material comprising that surface to a shape corresponding to the knurls on the outer surface of the impression insert 10. After the the impression insert has cooled, pressure is released from the handle 19 and the tool is withdrawn from the finger cavity 23, leaving knurls at the desired position therein. The tool may be used with finger cavities of various sizes by using appropriate inserts for each size since the diameter for each insert may be defined by the diameter of the finger cavity for which it is intended. Impression inserts with knurling of various designs may be used with this tool to produce a variety of gripping patterns; by varying pressure on the handle 19 of this device various depths of impressions may be formed. The operation of this device does not change the center of gravity of the bowling ball in which it is used since an inward displacement of any remoulded particle requires the outward displacement of some other particle within the same surface. Since pressure is applied only against softened material there is little danger in the development of weaknesses or cracking within the interior of the bowling ball.

A draw pin 14 of cylindrical shape and of size to be The invention is not limited to the exemplary construction herein shown and described but may be made in various ways within the scope of the appended claims.

What is claimed is:

1. A tool for knurling finger cavities in bowling balls, said tool comprising a draw pin having a base end and in cluding an outwardly and downwardly beveled surface therearound, a tubular mandrel slidably' mounted on said draw pin,;said mandrel having a downwardly and inwardly inclined beveled surface around the end thereof opposite the beveled surface of said draw pin, arcuate semicircular inserts positioned between the beveled surface of the mandrel and the beveled surface of the draw pin, at least one of said inserts having a knurled surface thereon, the respective upper and lower ends of said inserts having inclined surfaces corresponding with the beveled surfaces of said mandrel and said draw pin, and means moving the mandrel towards the base of said draw pin when said tool is inserted in a cavity of a bowling ball.

2. A tool as defined in claim 1 and wherein said means 4 moving said mandrel toward the base of the draw pin is comprised of cam rotatably mounted on said draw pin and arranged to engage the upper or outer end of said mandrel.

3. A tool as defined in claim 1, and wherein said means moving said mandrel is comprised of threads on the upper or outer end of said draw pin and a nut threadedly en gaged thereon and adapted to engage said mandrel.

References Cited in the file of this patent UNITED STATES PATENTS 447,011 Harman Feb. 24, 1891 950,838 (Iavanagh Mar. 1, 1910 1,253,463 Brown Ian. 15, 1918 1,447,059 Benson Feb. 27, 1923 1,723,785 Johnson Aug. 6, 1929 2,448,316 Lesavoy Aug. 31, 1948 2,541,358 Hirsch Feb. 13, 1951 

